The invention relates to a method for the manufacture of bristle material for brushes with different types of plastic bristles produced as continuous monofilaments by extrusion.
In the present context the term brushes applies to all products in which more than one type of bristle undergoes processing to brushes, brooms, scrubbing brushes, paint brushes, brushing belts, mats with a bristle facing, etc. Bristle material is understood to mean any composition of bristles having a finite length, which is processed either directly or after further cutting to size to form the brush.
The bristles forming the bristle facing are usually identical in brushes, i.e. are made from the same material and have the same geometrical dimensions. The only differences which exist relate to the length. However, brushes are also known, in which the bristle facing comprises individual bristle bundles or packets with different types of bristles in the bundle or packet. The different nature more particularly applies to the bristle diameter or material. This is firstly intended to give optical effects, but also the different characteristics of the bristles can be utilized, so that different types of actions are produced when using the brush. The best known differences are provided by mixtures of natural and plastic bristles, the mixture mainly serving to partly replace the more expensive natural fibres, without having to completely lose the advantageous characteristics of the natural bristles. Such mixtures are more particularly known in connection with paint brushes and brooms.
Plastic bristles are produced from continuously extruded monofilaments, which are wound up after extrusion. Prior to winding or during a further rewinding, said monofilaments are generally stretched to give them the desired bending behaviour. The molecular longitudinal orientation attained on stretching is optionally fixed by thermal stabilization. The monofilaments are then combined into strands and from the latter are cut tufts or knots, whose length is a multiple of the length of the subsequent bristles. These tufts surrounded with an envelope are subsequently cut into short-cuts, whose length roughly corresponds to that of the bristles. The short-cuts enclosed by the envelope are then used in brush manufacture, where the envelope is separated and the bristles are generally transferred to a magazine. From said magazine by splitting off individual bundles are removed and are then fixed to the carrier or support by a mechanical or thermal process.
In order to obtain with this procedure a bristle facing of bundles or packets with different types of bristles, the tufts or short-cuts with different types of bristles are horizontally positioned in juxtaposed manner after removing the envelope and are transversely mixed by coating over several times, after which they are again brought together and bundled. The composition and/or homogeneity of the mixture is largely left to chance and is generally completely inadequate. In addition, on mixing there is an undesirably high bristle material wastage. However, this mixing procedure is also very expensive due to the high machine and time costs. The mixing of rough and uneven plastic bristles is only possible, if at all, with unacceptable waste levels due to the combing necessary for orienting the bristles in the transverse position. The mixing of smooth plastic bristles is problematical due to their good sliding characteristics. The brushes manufactured in this way are not of good quality, i.e. particularly with respect to the orientation of the different types of bristles in the bundle or in the entire bristle facing.
In another procedure the continuous monofilaments are processed directly from the reel, in that the monofilament strand, in which the monofilaments are present in a number corresponding to the subsequent bundles or facing, are directly removed at the place of manufacture. There the leading end of the strand is positioned, optionally simultaneously thermally fixed to the bristle carrier and then cut to a length corresponding to the desired bristle length from the continuous strand. This procedure does not allow the aforementioned mixing to be carried out.
The problem of the invention is to provide a method permitting the manufacture of brushes with different types of plastic bristles, independently of which of the two aforementioned procedures is used during the manufacture of the brush and at the same time leads to a reduction in the cost of the plastic bristle mixture and ensures a mixture with a clearly defined composition.
This purpose is achieved in accordance with the invention in that differing types of endless monofilaments are brought together in the direction of their longitudinal extension to form a mixed strand having a composition desired for the completed brushes, the mixed strand is wound up, and the bristle material needed for the production of the brushes is cut to length from the mixed strand.